> PS: the sequence a(n)=(n^2)!/n!^2/2 for n>1, > [1, 3, 5040, 18162144000, 538583682060103680000, ...] > seems not in OEIS, so I consider submitting it; > any useful comments are welcome. The sequence a(n)=(n^2)!/n!^2 is A088021. I'm not saying you shouldn't submit it, just providing information. - Michael